Generally, a refrigerating system includes a compressor, a condenser, a drier, an expansion device, and an evaporator connected to one another by refrigerant pipes so as to circulate a refrigerant. While passing through the compressor, the condenser, the expansion device, and the evaporator, a refrigerant is compressed, condensed, evaporated, and expanded thereby to perform a cooling operation.
In the conventional art, one evaporator is provided, and a process for cooling a plurality of cooling spaces is performed by circulating cool air generated from the evaporator. However, recently, a refrigerating system for independently cooling a plurality of cooling spaces by using a plurality of evaporators is presented. The refrigerating system is applied to a refrigerator.
According to the refrigerator, a refrigerant is supplied to one of a plurality of evaporators thus to perform a cooling operation for a cooling space having the evaporator. Here, if the cooling space satisfies a condition preset by a controller, the refrigerant is supplied to another cooling space thus to perform a cooling operation.
However, the refrigerating system for independently cooling a plurality of cooling spaces by using a plurality of evaporators has the following problems. After one cooling space is cooled by one evaporator provided thereat, another cooling space is cooled by another evaporator provided thereat. Here, since the respective evaporators have different outlet temperatures from each other, a refrigerant remaining at the one evaporator is not sucked to the compressor at the time of a cooling operation. Accordingly, required is a ‘pump-down’ operation for collecting a refrigerant remaining at an evaporator to a compressor by operating the compressor under a state that refrigerant supply to a plurality of evaporators is blocked.
In the refrigerating system for performing a cooling operation by sequentially introducing a refrigerant into a plurality of evaporators, when a refrigerant remains at the evaporators, a cooling operation is performed with a refrigerant deficient by the remaining amount. Accordingly, the entire cooling operation is degraded. The ‘pump-down’ operation is performed to prevent the entire cooling capability from being degraded.
Especially, the ‘pump-down’ operation is required at the time of converting a cooling operation from a freezing chamber to a refrigerating chamber.
However, the conventional ‘pump-down’ technique has the following problems. First, a refrigerant remaining at the evaporators is collected to the compressor by operating the compressor under a state that refrigerant supply to the evaporators is blocked. Accordingly, as the ‘pump-down’ operation is performed, the compressor may have a lowered suction pressure and discharge occurrence. As a result, the compressor may have damage or a loss.
Second, in order to collect a remaining refrigerant to the compressor, a suction pressure of the compressor has to be excessively lowered. Accordingly, high power is required to operate the compressor, thereby degrading the efficiency of the refrigerating system.
Third, as the ‘pump-down’ operation is performed, a suction pressure and an outlet pressure of the compressor are lowered, and thus the collected refrigerant may backflow to the evaporator. To solve the problem, a backflow preventing unit is provided between a compressor inlet and an evaporator outlet, thereby increasing the fabrication cost.